In the scrubbing of flue gas for the removal of its sulfurous content, the gas is passed counterflow to a spray of finely ground limestone in a water slurry from nozzles designed to deliver solid-cone sprays of the slurry downwardly into a reactor vessel through which the hot flue gas from a boiler is passed upwardly. As the sprayed slurry is reclaimed from the bottom of the vessel and recirculated to the nozzles at the top, it is common experience that, in time, the solid materials in the slurry tend to agglomerate and form hard solids of substantial size which can easily clog nozzles of known types for the production of solid-cone sprays.
The problem of nozzle clogging has heretofore been approached in various ways. For example, in the nozzle of U.S. Pat No. 1,510,174, the liquid entering the nozzle body is deflected into a swirling eddy flow by deflector vanes extending radially into the nozzle body from its walls. The problem of clogging is referred to by reference to its solution in that patent, namely, the mounting of the deflector vanes so as to be rotatable about their own axes into axial alignment with the liquid flow to permit the flushing of obstructions and debris collected by the vanes which extend into the nozzle body from its four quadrants.
In addition, the nozzle of U.S. Pat. No. 1,510,174 mounts its flow-directing vanes in a turret within the nozzle body which, while incidentally enabling the nozzle to serve as a stopcock, can also be further rotated to reverse the flow path through the turret to flush the accumulated debris from the flow-directing vanes.
A more recent effort, illustrated by U.S. Pat. No. 4,494,698, addressed specifically to spray nozzles for abrasive slurries, molds the wall-supported flow-directing vanes of flexible polyurethane. This approach seeks to inhibit clogging by permitting deflection of the vanes in order to pass the solid agglomerates inevitably encountered.
While the earlier patent addresses the clogging problem by facilitating maintenance of the nozzle, the later acknowledges the impracticability of shutting down a combustion gas scrubber for nozzle maintenance.